Components in a mobil phone are tiny tiny tiny ... just how good are your desoldering skills?
The interface for the cameras is highly special and usually undocumented but the challenge is getting to those tiny legs. CORRECTION: A bit of googling found this little circuit diagram of the 6600 - and there is a pinout for the camera.
A mobile phone has several microphones (to elliminate the background noise) and uses advanced processing to undo the distortion of the sound of the microphones in their peculiar location. See if you can find them ;)
For common mobile phones there are some hacks out there how to reuse their displays (in particular when you can buy them as spare parts).
In short, the SD and SIM card holders, and the display, is resuable, but probably not the rest.